Development of Induction Brazing System for Sealing Instrumentation Feedthrough Part of Nuclear Fuel Test Rig

Hong, Jintae; Kim, Ka-Hye; Heo, Sungho; Ahn, Sung-Ho; Joung, Chang-Young; Son, Kwang-Jae; Jung, Yang‐Il

doi:10.3795/ksme-a.2013.37.12.1573

Cited by 2 publications

(1 citation statement)

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“…Following a series of publication from the Korean Nuclear Institute (KAERI) [12,13] we got additional valuable pieces of information directly from the authors. We learned that KAERI specialists do a large amount of work for qualification : (a) Fabricate more than 30 specimens using the stabilized optimal brazing condition (b) NDE (helium leak test or hydraulic pressure test) for all specimens (c) Tension test (showing only 80% of the ultimate strength of 'fresh' TC).…”

Section: Discussionmentioning

confidence: 99%

Issues in Manufacture and Qualification of Specialty Brazed Joints for Nuclear Applications

Truta

Ciocanescu

Amzoi

2016

AMR

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Nuclear experimental instrumentation frequently includes the usage of thin-walled (metallic sheathed) thermocouples passing through the boundaries of pressure vessels. This is accomplished by sealing the thermocouples by brazing through special design fittings (passages) which are later sealed / welded to the body of the vessel.Two are the challenges to face : (a) the manufacture of the instrumented passage (b) its mandatory qualification, according to relevant standards. Even the brazing qualification standards are more flexible than for welding, the peculiar situation of nuclear instrumentation still needs special consideration and it is not properly covered by the regular standards.The paper describes the experience of the authors in manufacture of the instrumented passages with steel or Inconel sheathed thermocouples, along with some other known projects, in conjunction with applicability of relevant standards: ASME code, AWS standards, national standards. Since it is about pressure vessels, ASME prescriptions are mandatory in Romania; other standards may serve as valuable sources for the “engineering judgment” allowed and recommended by ASME code.The main problem in such specialty brazing qualification is that for some combinations of base metals and filler (imposed by application), one cannot avoid the significant fragilization due to a tremendous increase of hardness in the brazing area. Base material erosion is added and the effect is catastrophic : sectioning the thermocouples at the slightest movement. For example, brazing Inconel thin-walled tubes with BNi-7 is very hard to control – experimental data and images are included in the paper to illustrate this.Therefore, special means must be applied both in fabrication and in qualification, in order to ensure the product is functional and safe, even being fragile. This approach can be found in French design of irradiation devices, being also considered in the French code for design and construction of experimental reactors and irradiation devices. Being known that French experience in this field is vast, their approach makes us confident that our brazing technique is not wrong but the problem is to be solved through ‘smart’ design and specific procedures. Consequently a tentative set of domestic rules for work and qualification is proposed for discussion and further improvement.

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Section: Discussionmentioning

confidence: 99%